Sometimes, during conservation, after filling a container with green tea beverage, a floating, cloudy, flocky (flocculent) or precipitate-like sediment (hereinafter, these will be collectively referred to as simply “sediment”) occurs. For green tea beverages filled in transparent containers, the occurrence of such type of sediment is as important an issue as it can lead to the loss of its market value.
Although generally referred to as “sediment,” it can be divided into “primary sediment,” which starts precipitating immediately after manufacturing the beverage, and “secondary sediment,” which occurs gradually with time after manufacturing the beverage, during storage. Among these, primary sediment is generally referred to as tea cream, which has been confirmed to be generated by binding of caffeine, tea flavin, and the like, and has been verified to be preventable by performing centrifugation, enzymatic treatment, membrane filtration, and the like in combination. On the other hand, secondary sediment is a greater problem than primary sediment, for which various preventive methods have been proposed in the prior art.
A method for eliminating the substance causing the sediment has been proposed as one preventive method of secondary sediment. For instance, a method has been disclosed wherein tea is extracted with warm water, the obtained tea extract is cooled prior to adding tannic acid and let to stand still, followed by centrifugation and the like to remove fine tea particulates, and thereafter clarified by kieselguhr filtration (Japanese unexamined patent publication No. H6-269246).
In addition, a method has been disclosed wherein tea extract resulting from the extraction of green tea is acidified by adding ascorbic acid, then rapidly cooled and centrifuged prior to performing kieselguhr filtration for clarification (Japanese examined patent publication No. H7-97965).
Furthermore, a method has been disclosed wherein chitosan is added to a tea extract of a water-soluble tea component obtained by extracting green tea with water or hot water, macromolecular component polyphenols are sponged by adsorption, then this is processed by a centrifuge and further kieselguhr-filtrated to eliminate generation of precipitates (Japanese unexamined patent publication No. H6-311847).
In addition, a method has been proposed wherein a chemical reagent, an enzyme, and the like are added to solubilize or stabilize insoluble complexes (sediments). For instance, a method that effectively inhibits the occurrence of secondary precipitation in green tea beverages, wherein the warm-water tea extract from green tea is centrifuged or cloth-filtered, combined with a step wherein an enzyme having hemi-cellulase activity is further added (Japanese unexamined patent publication No. H8-228684), a method that inhibits the occurrence of flocks in beverages by adding α-amylase to the green tea extract (Japanese unexamined patent publication No. 2001-45973), a method for manufacturing green tea beverages wherein enzymatically treated lecithin, such as lysolecithin, is added to and mixed with the green tea extract to inhibit the occurrence of opacification or precipitations (Japanese unexamined patent publication No. 2001-204386), and the like have been disclosed.
However, the methods that intend to prevent secondary sediments by removing the substances causing the sediments bear the problem that since they ultimately eliminate all the substances causing opacification/precipitation contained in green tea beverages, ingredients that influence tea flavor and are not involved in sediment formation are also eliminated in large quantities, weakening the original flavor of the tea.
In addition, methods that solubilize or stabilize insoluble complexes by adding chemical reagents or enzymes have the problem that the original flavor of the tea is altered by the reaction between the additives and the contained ingredients.